This invention relates in general to controlling pressure with an electronic engine controller. More particularly, the present invention relates to a system and methods for precisely controlling the pressure generated by a blower coupled to an engine by electronically controlling the engine speed.
Control of engine revolutions per minute (RPM) by mechanical means is well known. One such embodiment is by means of controlling the throttle of the engine with adjustable spring tension. For example, a centrifugal device may be mechanically coupled to a moving component of the engine to provide a representation of the RPM of the engine. When centrifugal forces in the centrifugal device are in balance with the spring tension, the throttle remains fixed. However, when the centrifugal forces and the spring tension are not in balance, the throttle is either opened or closed to achieve balance.
This throttle arrangement functions well for some applications. However, where the engine controller is used to control liquid or pressure developed by a blower coupled to the engine at a nozzle, the nozzle pressure is not usually directly related to engine RPM. That is, constant engine RPM will not necessarily result in constant gaseous or liquid pressure. In addition, nozzle pressure is subject to a variety of variables including temperature, humidity and barometric pressure. Nozzle pressure may vary by as much as 20 percent due to these variables when the engine RPM is kept constant.
There is therefore a need for an improved engine controller that can effectively control and maintain nozzle pressure rather than engine RPM.